The following description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art, or relevant, to the presently claimed inventions, or that any publication specifically or implicitly referenced is prior art.
This application relates to retroviral vectors, particularly trans-lentiviral vectors, for the efficient and stable transduction of cells with heterologous nucleic acid sequences.
Lentiviral vectors are able to transduce nondividing as well as dividing cells and sustain expression of heterologous nucleic acid sequences in several target tissues in vivo, including brain, liver, muscle, and hematopoietic stem cells. Miyoshi et al. (1999) Science 283:682-686; Kafri et al. (1997) Nature Genetics 17:314-31; Akkina et al. (1996) J. Virol. 70: 2581-2585; Naldini et al. (1996) Science 272:263-267. Lentiviral vectors therefore hold great promise for gene therapy, and clinical trials to evaluate their safety and efficacy for treating certain human diseases are being considered. Amado et al. (1999) Science 285:674-676. However, and despite this promise, there remains a concern for safety insofar as lentiviruses are known to cause disease.
To address this, so-called “split-function” vector systems have been designed that express the essential lentiviral genes (gag, pol, and env) on separate genetic elements. Naldini et al., supra; Kafri et al. (1999) J. Virol. 73:576-84; Wu et al. (1997) EMBO, 16(16):5113-5122. The in trans “piecemeal” supply of these coding elements to a packaging cell allows for the production of infectious viral particles having the ability to transduce cells, but otherwise having a reduced potential for genetic recombination and the establishment of new infection, i.e., integrated recombinant proviral DNA. Still, the possibility exists that replication competent retroviruses (RCRs) and accompanying pathology can result from genetic recombination.
There is thus a continuing need for improved lentiviral vector systems that afford relatively high vector particle production, improved transduction capabilities, and which have even lower potential for RCR events.